The present invention relates to novel compounds derived from sugar, to processes for preparing them and to their uses as surfactants.
During its research directed towards preparing surfactants capable of producing vesicular emulsions or inverse micelles, the Applicant noted that some of these bicatenary compounds made it possible to produce emulsions of this type.
Accordingly, a subject of the invention is a compound of formula (I):
ROxe2x80x94(X)pxe2x80x83xe2x80x83(I) 
in which:
p represents a decimal number between 1 and 5 and
X represents a xylose residue, and
R represents a branched alkyl radical:
CH(CnH2n+1)(CmH2m+1)xe2x80x94CH2xe2x80x94
in which m is an integer between 6 and 18, n is an integer between 4 and 18 and the sum n+m is greater than or equal to 10.
The oligomeric structure (X)p may be in any isomeric form, whether of optical isomerism, geometrical isomerism or positional isomerism; it may also be a mixture of isomers.
In formula (I), the group Rxe2x80x94Oxe2x80x94 is linked to X by the anomeric carbon of the saccharide residue, so as to form an acetal function.
p, which represents the average degree of polymerization of the saccharide, is more particularly between 1 and 2.5 and most particularly between 1 and 2.0.
According to a first particular aspect of the present invention, one subject thereof is a compound of formula (I), as defined above, in which n and m are even numbers.
According to a second particular aspect of the present invention, a subject thereof is a compound of formula (I), as defined above, in which the sum n+m is equal to 10. In this case, R more particularly represents a 2-butyloctyl radical (n=4, m=6).
According to a third particular aspect of the present invention, a subject thereof is a compound of formula (I), as defined above, in which the sum n+m is equal to 12. In this case, R more particularly represents a 2-butyldecyl radical (m=4, n=8) or a 2-hexyloctyl radical (m=6, n=6).
According to a fourth particular aspect of the present invention, a subject thereof is a compound of formula (I), as defined above, in which the sum n+m is greater than or equal to 14. In this case, R more particularly represents a 2-hexyldecyl radical (n=6, m=8), a 2-hexyldodecyl radical (m=6, n=10), a 2-octyldecyl radical (m=8, n=8), a 2-octyldodecyl radical (m=8, n=10), a 2-decyltetradecyl radical (m=10, n=12), a 2-dodecylhexadecyl radical (m=12, n=14), a 2-tetradecyloctadecyl radical (m=14, n=16), a 2-tetradecyleicosyl radical (m=14, n=18), a 2-hexadecyloctadecyl radical (m=16, n=16) or a 2-hexadecyleicosyl radical (m=16, n=18).
A subject of the invention is also a process for preparing a compound of formula (I) as defined above, characterized in that the xylose of formula (II):
HOxe2x80x94Xxe2x80x83xe2x80x83(II) 
is reacted with an excess of alcohol of formula (III):
ROHxe2x80x83xe2x80x83(III) 
to form, after removal of the unreacted fatty alcohol of formula (III), the compound of formula (I).
In the process as defined above, the reaction for formation of the compound of formula (III) is carried out in the presence of strong acid catalysts such as, for example, mineral acids, for instance sulphuric acid or hypophosphorous acid or a mixture of these acids.
According to one variant of the process as defined above, the xylose of formula (II) is reacted with an alcohol of formula (IV):
R1xe2x80x94OH 
in which R1 contains from 1 to 4 carbon atoms, and more particularly with butanol, to give the acetal of formula (V):
R1Oxe2x80x94(X)pxe2x80x83xe2x80x83(V), 
this acetal of formula (V) then undergoing a transacetalization with an excess of alcohol of formula (III) with distillation of the alcohol of formula (IV) formed, followed by removal of the unreacted alcohol of formula (III).
In the process and its variant, as described above, the removal of the unreacted alcohol of formula (III) is carried out according to methods that are known to those skilled in the art, such as, for example, distillation, thin-film distillation, molecular distillation or solvent-extraction.
The compound of formula (V) by itself constitutes another aspect of the present invention.
According to another aspect of the present invention, a subject thereof is a composition (A), consisting of a mixture of at least two compounds of formula (I) which may be obtained by the process or its variant as are defined above, using a mixture of alcohols of formula (III) instead of only one of these alcohols of formula (III).
According to another aspect of the present invention, a subject thereof is a composition (B), characterized in that it comprises:
more than 0% by weight and less than 100% by weight, preferably from 1% to 60% by weight, of a compound of formula (I) or of a mixture of compounds of formula (I), as defined above, and
more than 0% by weight and less than 100% by weight, preferably from 40% to 99% by weight, of a compound of formula (III) or of a mixture of compounds of formula (III), as defined above.
The composition B as defined above is prepared, for example, by reacting an excess of compounds of formula (III) with xylose according to the process or its variant as are defined above, without removal of the unreacted alcohols of formula (III). It may also be obtained by mixing an alcohol of formula (III) or a mixture of alcohols of formula (III) with a compound of formula (I) or a mixture of compounds of formula (I).
The chain(s) R of the compound(s) of formula (III) is (are) preferably identical to those of the compound(s) of formula (I).
According to a final aspect of the present invention, a subject thereof is the use of a compound of formula (I), of a composition (A) or of a composition (B), as described above, as a surface agent or surfactant, and more particularly the use as an emulsifier when the sum n+m is greater than or equal to 14 and as a foaming agent, wetting agent, detergent agent or antifoam solubilizing agent, when the sum n+m is less than 14.
The examples which follow illustrate the invention without, however, limiting it.